This invention relates to a new and improved axial magnetic field high voltage vacuum interrupter for interrupting the flow of electrical current in high voltage electrical circuits.
A high voltage vacuum interrupter is a type of circuit breaker or switch that is used to interrupt the flow of large currents. As used herein, the term "high voltage" refers to a voltage greater than 1,000 volts. A high voltage vacuum interrupter is disclosed in U.S. Pat. No. 4,568,804 to Elmer Luehring. The vacuum interrupter has a pair of terminals each of which is connected to a respective switch contact, one of which is stationary and one of which is movable. The switch contacts are provided in a vacuum chamber to minimize electrical arcing when the switch contacts are moved away from each other to interrupt the flow of electrical current.
Conventional high voltage vacuum interrupters have a limit to the amount of current they can interrupt due to electrical arcing since larger currents are more likely to cause sustained arcs when the switch contacts are separated. Some high voltage vacuum interrupters have been designed to generate an axial magnetic field to increase the amount of electrical current they can interrupt. The axial magnetic field helps to prevent the formation of a narrow, constricted electrical arc between the two switch contacts, thus increasing the current-interrupting capability of the interrupter.
Axial magnetic field vacuum interrupters typically include switch contacts that are provided with a current carrying tube-shaped copper cylinder having slots cut therein so that the current flows through the cylinder in a helical path to generate the axial magnetic field. One example of such a vacuum interrupter is disclosed in U.S. Pat. No. 4,695,687 to Grosse, et al.
Switch contacts produced by cutting slots in a preformed copper cylinder are relatively expensive to produce for a number of reasons. The slotting operation is relatively complicated and requires the use of relatively expensive machining apparatus. The copper cylinder in which the slots are cut is relatively expensive, and the copper removed from the cylinder by the slotting process is wasted. The complicated nature of the slotting procedure also reduces the flexibility to manufacture switch contacts of different sizes and having different electrical characteristics.